Propeller pitch changing mechanism



June 23, 1953 Filed Oct 20, 19443 E. MARTIN EVAL PROPELLER PITCH CHANGING MECHANISM 2 Sheets-Sheet 1 June 23, 1953 E. MARTIN ETAL 2,642,945

PROPELLER FITCH CHANGING MECHANISM Filed Dot. 2o, 1945 2 sheets-sheet 2 Patenied June 23, 1953 VifnizonilNTsM l Erle Martin, West Hartford, Murray C. Beebe, Jr., South Glastonbury, and John E. Anderson, Portland, Conn., a'ssignors to United Aircraft CorporationgEast Hartford, Conn., a. corporation of. Delaware Application october 2o, 1943, serial No. 506,983

rlhis invention relates to improvements in hydraulic mechanisms and has particular reference to an improved hydraulic mechanism for chang- 'ing the pitch of a controllable-pitch propeller;

An object of the invention resides in the provision of means 'for' accumulating hydraulic fluid under pressure at times When the entire supply of such fluid is notrequired to operate the mechanism and for releasing the accumulated fluid at times when an amount of hydraulic lfluid greater than the capacity of the normal supply at that time is required by the mechanism.

A further object resides in the provision, in combination with a hydraulic motor anda pump for supplying hydraulic iiui'd under pressure for operating'said motor, of pressure fluid-accumulating-means arranged to receive fluid under pressure from the pump when the requirements of the hydraulic motor are less than the output capacity of the pump and to discharge fluid under pressure to the motor when the requirements of the motor exceed the immediate capacity of the pump.

A still further object resides in the provision otra pitch changing mechanism for av hydrocontrollable propeller provided With means for accumulating a reserve'of fluid under pressure to accelerate the operation of the pitch changing mechanism.

An additional 'object resides in the provision of means for storing hydraulic iiuid under pressure during operation of the propeller and for retaining this fluid Iunder pressure during such time as the Vpropeller is in a feathered condition in order to provide a source of fluid under pressure to return the propeller from its feathered condition. y

Another object resides in the provision of valve means effective tc unload the pump Whenever the pressure of the fluid in the high pressure portion lof the system reaches a predetermined value2 Other objects and advantages will be more particularly pointed out hereinafter or will become apparent as the description proceeds.

In the drawings there is illustrated a suitable propeller pitch changing mechanism, anda co-nf 11 claims. (ol. 17o-160.2)

trol therefor, forfthe purpose of disclosing the invention.

Fig. l is a diagrammatic illustration of a hydrocontrollable-pitch propeller and control means therefor showing the application thereto of an accumulator and accumulator control means constructed and arranged according to the invention..

Fig. la is an enlarged View partly in section of uthe accumulator valve control. i

Fig. 2 is affront-elevational view of a propeller vhub showing theapplication thereto of accumulators constructed according to the invention, one of the accumulators being shown in'section to better illustrate theconstruction thereof, and

Fig. 3 is an enlarged sectional vieW of a portion of the accumulator.

y The propeller,generally indicated at lll, has one or more pitchv changing fluid motors, such .as the vane-type motor generally indicated at l2, carried Yby thepropeller hub Hi and operatively connected With the propeller blades, two of Which'are indicated at l5 and i8, for changing the pitch of the propeller. Fluid under pressure for'operating the pitch changing motors is delivered by a pump,generally indicated at 20, mounted on, and rotatable with, the propeller hub and having plungers 2| actuated by a stationary cam 22 supported on a member such as the engine nosepiece 24, in such position that propeller shaft 25 extends through the cam. With this arrangement, as the propeller rotates relative to the fixed cam, plungers 2| will be actuated to Withdraw uid from the annular sump or reservoir 28 and deliver it under pressure to the annular manifold 30. Sump 28 is connected through achanne1 32 with a vent control valve, generally indicated at 34 (Fig. l) and having a plunger 33 urged to valve closing position by spring 3l. The inlet of this valve 34 isY from the interior of the propeller hub which is utilized as an auxiliary sump and is maintained full of hydraulic iluid at a relatively low pressure as determined by valve 34 to insure an adequate supply of lubricating oil for the Working parts Within the propeller hub. A portion of the interior of the propeller hub is diagrammatically indicated at 35 in Fig. 1 in connection with the showing oi valve 34. A cylindrical distributing valve 35 carried by the propeller hub, for controlling and determining the propeller pitch, has two ports 33 and 4E! connected with the interior of hub 35 by channels 4l and 41. The valve also has a port 44 connected through channels 42 and d5 with the discharge Yside of a check valve 5l), the inlet side of which is connected With manifold 30. The opposing sides of motor I2 are connected through channels 52 and 56 with ports 54 and 58, respectively, in the casing of valve 35. Valve 35 includes a folloW-upvalve in the form of a sleeve B0 slidable in the valve casing and having ports which can register with Vthe above-mentioned ports. Within sleeve 5E! is a slidable pilot valve 62 having a pair of lands 64 and 55. Land 64 controls the connections Within the sleeve hetween port 58 and ports 38 and 44, while land |55 controls the connection between port 54 and ary cam 22 and having on its other end a shifterr ring i4.

generally indicated at 18.

The movable outer portion'lof apitch changing motor I2 is provided with a cam 80 which" serves to move sleeve 60 longitudinally by means of a lever 82, pivoted at 84, attachedtoA sleeve-60. at:

Elements 10, 12 and 14 form aA unit` constrained to rotate with shaft 26 by a key. 16, which, however, permits longitudinal adjustment of the unit, and of pilot valve 625, by:atservo-rrnot'or,l

A booster pump I I8 is driven from shaft I I2 by means not illustrated, and is connected to reservoir |20 by suction pipe |22. The outlet II9 of pump ||8 is connected to pressure relief valve |24, and governor valve- I I4. Theoverilow from relief valve |24, is returned tog, reservoir |20 through channel |22. A fluid channel |26 leads 'from the governor valve to the lefthand end of the servo-motor actuating cylinder 96 to admit `fluid under pressure thereto and force the piston 98 to the right against the force of the spring or to vent. fluid from the cylinder 96 to permit'spring |00 to move piston 98 and shaft 92 tothe left.. Hydraulic fluid is supplied to thefcylinder 9|iA when the governor valve II4 is in itsl raisedposition and connects channel |26 Y with the pump outlet II9. Fluid is vented from 86, and having a contact shoe 88 heldagalnst motor I2 connected therewith, and port 54 will be connected with port 40 permitting fluid to drain from the opposite side of the motorv through channels 52 and 41, to hub interior 35, and thence through valve 34 to sump 28,-when the' pressure of the fluid in the hub is sufficient to operate valve 34.

As the pitch changing vmotor rotates under these conditions to change the propeller pitch, cam 80 and lever B2 will move sleeve 60 to the left to follow-up the movement of pilot valve 62, t

and when the pitch has been changed by an amount corresponding to the movement of the pilot valve, ports 54 and 58 of sleeve valve 60 will be brought into registry with pistons 66 and 64 thereby blocking channels 52 and' 56 and preventing further rotation of'pitch changing motor I2. If, because of yleakage of fluid in the motor or valve, the pitch tends to change, sleeve 60 will be moved to reopen theports, admitting sumcient fluid under pressure to restore the pitch to the angle corresponding'to the instant position of pilot valve 62. If the servo-motor again moves pilot valve 62 motor I2 will again beoperated to change the pitch to a new angle corresponding to the new position of the'plunger so that the pitch angle of the propeller has at all times a value corresponding to the: positiony ofl pilot valve 62.

If plunger 62 is movedv to the right; channel 52 will be connected with pressure-line 42 and l channel 56 will be connected with interior135 of the propeller hub through channels 4I, 41- to change the propeller pitch inv the; opposite direction.

Servo-motor 18 comprises an operating cylinder 96 containing a piston 98 secured 'on the shaft 92 and movable in both directions over a range corresponding to the range of pitch adjustment of the propeller. A compression spring I 00 constantly urges shaft' 92 and piston 98 toward the left.

A governor, generally indicated at |02 controls the operation of servo-motor 18 and has a pair of ilyballs |04 mounted on. a flange |06 integral with a rotatable sleeve propeller shaft 26 by gear |:I0 and shaft ||2. Within sleeve |08 is aplunger II4, constantly urged upwardly'by ilyballs |04'.v Upward movenfnt of the plunger is resisted by Speeder spring I cylinder 96 when valve II4 is in its lowered position and connects channel |26 with reservoir |20 around the lower end of valve ||4 in the enlargedboreof sleeve I 08.

As piston 98 of servo-motor 18 is connected withpilot valve 62 which determines the propellerv pitch, the governor thus controls the propeller pitch by actuation of servo-motor 10 to provide constant speed control.

Manually operated means |28 is provided for :manually controlling the propeller pitch, especially for feathering and unfeathering. This manually operated means comprises a lever pivoted at |32 on a ilxedl support |34 and has a. releasable detent |36 `at one end and is connected with rod |38 at the other end. RodA |38 -is notched to permitnormal movement of piston 98 but when moved itself, coaots with flange connected with servo-piston 98. When moved to the right, rod |38 will move piston 98, shifter ring 14 and pilotvalve 62 to the right, against the forceofl spring |00, and thus admit fluid,v under pressure to pitch changingmotors I2 and increase the propeller pitch. Sufficient movement of rod |38 to the right will feather the propeller. When the propeller is in feathered position, movement of rod |38 to the left will move'pilot valve 62 to the left and admit iluld under pressure to the opposite side of pitch changing motors I2 and cause the propeller to unfeather.

As the propeller does not rotate when feathered andv hence pumps 20- are not effective to provide fluid pressure another source of fluid under pressure is required to return the propeller from its feathered condition to a pitch angle at which rotation is resumed with consequent resumption of operation of the pumps, 20. Such a source of hydraulic fluid under pressure may be provided by the accumulator or accumulators one of which is shown in Figs. 1 and la and generally indicated by the numeral |40, and .three of which are shown in Fig. 2 and indicated at I40a, |40b, and |40c. These accumulators may also supply the necessary energy to fully feather the propeller in the event the propeller pump 20 is slowed down by decrease in engine speed, before the propeller is fully feathered, toa speed at which it is unable to supply the necessary quantity of fluid at the necessary pressure to complete the feathering operation.

The accumulators are rigidly mounted on the propeller hub and may conveniently be positioned in the spaces between the propeller blade roots, as it particularly shown in Fig. 2. In this figure, the blade sockets are indicated at |42a, I42b, and I42c andmay contain the pitch'changing motors.

A pressure channel |62 leads'from the check valve discharge channel 46 around the propeller hub interconnecting all of the accumulators |46. This line |62 leads, at the locations of the pressure accumulatore, to respective cavities one of Which is indicated at |64, to provide pressure fluid connections for the various pressure fluid accumulators.- Y

The maximum pressure of the hydraulic fluid from the pump 2 is lcontrolled by a pressure relief valve generally indicated at |46. The relief valve has a reduced valve-operating plunger |68 and pressure fluid from the cross channel 46 is applied to the end of this plungerto move it against the force of a compression spring |56 w/hen the'fluid pressure in the line 46 exceeds a predetermined value.

check valve 56 to a side' port v|54 in the valve |46 controlled by a piston |56 operated by the plunger |46. 'A drain passage |58leads from a 'port |66 oppositev the port V|54 tothe interior 35 of the propeller hub from which the fluid may .be discharged through thc valve 34 to the sump E8 as previously described.

With this arrangement, when the fluid pressure in the high pressure side of the hydraulic system, including thepressure fluid accumulators, has been built up to a predetermined value, for example, two thousand five hundred pounds per square inch, the plunger |48 of the relief valve |46 will be moved to connect the line |52 with the drain passage |53 thereby unloading the pump 26 down to the pressure maintained by ,the valve 34 which pressure may be relatively low, for example, twenty-live pounds per square inch. The check valve 50 prevents the pressure' in channel 46 from feeding back into the pump or Ainto channel |52 so `that the pump will remain unloaded as long as there is sufficient fluid pressure in the high pressure portion of the hydraulic v system to maintain relief valveplunger Hill in position to connect channel |52 with vent passage E58. When the pressure in the yhigh pressure portion or the Vsystem decreases sufficiently to permit the` relief valve to close the channel |52 is blocked off and the pumpV outlet pressure builds up sufficiently to open the check valve'56 and increase the iluid pressure in the high pressure portion of the hydraulicV system until relief valve |46 is again forced open.

Reference may now be had to Figs. 2. and 3 for a detailed description of the pressure accumulators. 4As the accumulators are all identical, it is believed that adescription of only one of them is sufficient for the purpose of this disclosure.

Each accumulator comprises a cup-shaped metal casing |56 provided at its open end with internal screw threads which engage with external threads provided on an annular boss |66 surrounding the depression |64 and substantially` concentric therewith, a metal end closure and valve support generally indicated at |16 mounted within the boss |68 and a diaphragm |72 of rubber, neoprene, or some other resilient material impervious to fluids under pressure. The diaphragm H2 is provided at its open end with an threaded' opening containing .a valve plug `|.'|6

through which gas under pressure maybe inv A second line |52 leads from the pump outlet on the purnpside of the the accumulator.

troduced into the space between the casing |66 and the diaphragm |'||2,` A guard member' ii is provided at the inner end of this opening which prevents the diaphragm from being forced into ,thev openingand jamming the opening or from being injured. vWhen the device is in use, a gas, such asV nitrogen, at a relatively high pressure, for example, one thousand pounds per square inch, is forcedY into the casing |66 until the diaphragrn is collapsed against the inner side of the bottom member H6 anda substantial pres sure is built up in the casing |66.

The valve support generally indicated at H6 carries the valve lassemblyfor the accumulator. 'Ihe valve assembly comprises a casing |66 screw threaded into the support |76 and inturn supporting valverplungerlm and pilot valve |84. Valveplunger |62 is reciprocableA in a bore in casing |66 and has a valve' portion seating on casing '|36 and'closing thepassage |63 between the interior of the accumulator and the cavity l|66 on the exterior of theaccumulator. In order to balance the pressures acting onV valve plunger |62 and'reduce the operating forces, the plunger is provided with a pilot valve controlling a passage through the plunger and connecting the opposite sides thereof. The pilot valvelf, is'urged into closing position against the apertured end wall of the plunger |32 by a compression spring |86. This spring v|86 also acts to urge the valve plunger |82 to valve openingv position under certain conditions as will presently appear. Both thevalve plungerand the pilot valveare urged to closed position by a second compression spring |83 whichsurrounds the stem of the pilot valve and bears against the casing |66 and an abutment |66 secured on the end of the stem of the pilot valve. A pin |92 is interposed between theabutment |66 and a slidable cam member |94 reciprocably mounted in an aperture in the propeller hub and connected to flange lll of the hub l2; There is anindividual cam member for each accumulator.

A guard member IE6 is provided over the aperture leading through the bottom memberv |16 into" the interior of the diaphragm lf2. The guard members |13 and |66 are similar in construction and ,each 'comprises Va stem portion secured to the bottom member il@ or to the -casing |66, a dome shaped head portion overlying the adjacent surface of the corresponding casing orrbottom member and provided with shallow indentations toprovide` narrow fluid passages through which fluid may pass but which are so narrow that the diaphragm |'E'2 cannot be injured by being forced into these passages by fluid pressure.

In `all operating conditions of the propeller except the feathered condition, the cam member |94 is positioned so that the pin |62 is on lthe high portion of the cam maintaining the spring |66 under compression andholding the seats, thus opening a passage to the interior of Under these conditions, fluid under high pressure from the pump 20 flows to the chamber |64 formed between the portion of the propeller hub upon which the accumulator is mounted and the adjacent surface of the bottom member |16 through the channel |62 and ows through the channel |98 and past the guard member l|66 into the interior of the diaphragm |12. As the pressure of the pitch changing fluid l flowing to the above-mentioned chamber through `the fluid channel |62 is higher than the pressure of the. gas introduced between the,r casing' |166 and the diaphragm |12, this` gas will be compressed andthe diaphragm expanded until the fluid pressures on opposite sides ofjthe diaphragm are equal. Since the spring |86 is placed under compression by the pin |92 opening the pilot valve |84, the valve plunger |82- will beheld in its open position so that fluid may pass freely into and out ofthe accumulator. Fluid pressure on opposite ends of the plunger |82 is balanced by some of the fluid flowing past the pilot valve |84 and accumulating back of the plunger in the valve casing |80 so that. the plunger tends to remain steadily in its valve opening position. If now'they pressure of: the; iluid inthe channel |62 drops below the pressure of the fluid in the accumulator due to the fact; that operation of the pitch changing motor withdraws fluid from the high pressure side of the hydraulic system, fluid will flow from theA accumulator past the valve seat at the end of the casingv |80 and into the high pressure side ofy the hydraulic system to supply uid` under pressure in addition to the fluid under pressure; supplied by the pump 20. When operation of the pitch changing motor slows down or ceases the pump will again build up the pressure in the hydraulic system and the supply of fluid in the accumulator Will be replenished.

When the rod |38,` flange 'I0 and pilot valve 62 are moved to the right to propeller feathering position, the cam member |94 being fastened to flange 18 is also moved to the right so that pin |82 is in the low portion of the cam member, thus permitting the pilot valve |84 to be closed by springs |86 and |88. Fluidtrapped between plunger |82 and the closed' end of the bore in casing |80 will temporarily maintain the plunger |82 in Valve opening position. The trapped uid will leak out past the plunger permitting valve |82 to close Linder the influence of spring |88 and the accumulator pressure so that the valve plunger |82 moves to its closed position after the propeller is in feathered position and before there is an appreciable decrease in the pressure of the iluid within the accumulator. With the plunger |82 in valve closing position and the pilot valve closed as indicated above, and particularly illustrated in Fig. 3, fluid under pressure will be retained in the accumulator while the propeller is in its feathered condition. When rod |38 and flange 'l0 are moved by the manual control to the left to position valve E2 to return the propeller from its feathered condition to governor control as described above, the cam member |94" for each accumulator is moved to open each pilot valve and permit an equalization of fluid pressure at the opposite ends of the respective plungers |82 so that the springs |86 can move these plungers to the valve opening position after which high pressure fluid from the accumulators may flow into they hydraulic system to decrease the propeller pitch.

While a suitable metchanicalembodiment has been hereinabove described and illustrated in the accompanying drawingsl for the purpose of disclosingthe invention, it is to be understood that the invention is not limited to the particular embodiment so illustrated and described but that such changes in the size, shape and arrangement of the various parts may be resorted to as come within the scope of the sub-joined claims.

Having now described the invention so that others skilled inV the art mai/"clearly understand the samefwhat-it is desired tcL secure by Letters Patent isas follows; i

1. -In `a hydraulic system including, a motor, a pump for providing hydraulic fluid under pressure toA operate said motor and a fluid channel between said pump and said motoim-a fluid accumulator connected with said channel for receiving fluid under pressure from said pump, a pressure relief valve connected with said channel and containing a plunger movable by fluid pressure in said channel when said pressure exceeds a predetermined value, a check valve in said channel on the pump side of said relief valve and said accumulator, a vent passage leading from said relief valve andl a iluid channel leading from the outlet of said pump between said pump and said check valve to said relief valve at a location to be connected with said vent passage by' movement of said relief valve plunger by the application of fluid pressure thereto.

2. Hydraulic pitch changing mechanism for a propeller comprising a pitch changing motor, a pump operable by rotation of said propeller for supplying fluid under pressure for operating said motor, a valve between said pump and said motor controlling the flow of said fluid to said motor to control the operation of said motor, a followup connection between said motor and said valve for determining the propeller pitch by the position of said valve, a pressure fluid accumulator having a normally open outlet connected with said valve, means for moving said valve to a position to feather said propeller and a device movable with said valve for closingy the outlet of said accumulator when the valve is positioned to feather said propeller and to hold the outlet of said accumulator open when the valve is positioned to unfeather said propeller.

3. In a pitch changing mechanism for the blades of a feathering-type controllable pitch propeller, a pitch changing motor, a source of uid pressure dependent upon rotation of said propeller, a first conduit connecting said source with said motor, an accumulator for storing fluid under pressure, means connecting said accumulator with said motor means, including a device in said first conduit, for controlling the application of uid under pressure to said motor, said -device including means operably connected with said motor for positioning said propeller blades in accordance with the position of said controlling means, a normally open outlet for said accumulator, a valve controlling the outlet of said accumulator, and means operable by said controlling means for closing said valve when said device is in position to feather said blades.

4. In a pitch changing mechanism for a feathering-type controllable pitch propeller, a pitch changing motor, a pump operable by rotation o1' said propeller for supplying fluid under pressure to said motor for operating the same, a conduit connecting said pump. and said motor, an accumulator hydraulically connected with said pump and said motor for receiving and storing fluid-under pressure from said pump, a Valve controlling the outlet of said accumulator, a valve in said conduit comprising a manually movable part and a part movable by the propeller blades for positioning the blades in accordance with the position of said manually movable part, and meansv connecting said manually movable part with said accumulator outlet controlling valve to close said last-mentioned valve when said manually movable part is positioned to feather said propeller..

5. Pitch changing mechanism for a propeller comprising,r a pitch changing motor, a source of fluid pressure dependent upon rotation of said propeller, a connection between said motor and said source, an accumulatorcarried by said propeller, a normally open connection including a valve between said motor and said accumulator, pitch selecting' means havinga uid controlling means located in said connections on the motor side Yof said source and said accumulator, and means actuated by said selectingmeans for con'- trolling said valve and effective to close said valve and-prevent the applicationof fluidpressure from said accumulator to said motor While the pitch selecting-.means is in feathered position and the propeller is feathered.

6. Pitch changing mechanism for a propeller comprising, a pitch changing motor, a source of fluid pressure dependent upon rotation of said propeller connected with said motor, an accumulator carried by said propeller and having an outlet connected with said motor and said source, means preventing the return of uid pressure from said accumulator to said source, pitch selecting means having a mechanical connection with the propeller blades and including means for hydraulically positioning the propeller blades in accordance Wtih the position of said selecting means, and means actuated by said selecting means for controlling the outlet of said accumulator and the application of. iiuid pressure from said accumulator to said motor, including means for holding the outlet open during operation of the propeller and closing the outlet of said accumulator when said selecting means is in position to feather said propeller.

7. In a V,hydraulic pitch changing mechanism for a controllable pitch propeller, a pitch changing motor, a pump operable by rotation of said propeller to supply hydraulic fluid under pressure to operate said motor, means hydraulically connecting the outlet of said pump with said motor, means in said connecting means selecting the propeller pitch and controlling the flow of fluid to and from said motor, a pressure fluid accumulator having an outlet and continuously open to said connecting mea-ns, while said pitch selecting and flow controlling means is set to select an operative pitch position, to receive surplus fluid from said pump when the pump capacity is greater than the motor demand and return iiuid to said connecting means and the motor when the supply from the pump is less than the motor demand and. means for maintaining the fluid within the accumulator under pressure, a valve in said outlet and means for closing said valve when the propeller is feathered.

8. In a hydraulic pitch changing mechanism for a controllable pitch propeller, a pitch changing motor, a pump operable by rotation of said propeller to supplyhydraulic fluid under pressure to operate said motor, conduit means connecting the outlet of said pump with said motor, means in said conduit means selecting the propeller pitch and controlling the flow of fluid to and from said motor through said conduit means, a pressure fluid accumulator, an outlet for said accumulator, valve means in said outlet, means for holding said Valve means open While said pitch selecting and oW controlling means is set to select an operative pitch position and to receive surplus fluid from said pump when the pump capacity is greater than the motor demand and return fluid to said conduit means and the motor when the supply from the pump is less than the motor demandfand means actuated by said selecting meansfor controlling the outlet of said accumulator and the application of fluid pressure from said accumulator to said motor includingmeans for closing said Valve means in the outlet of said accumulator when said selecting means is in position to feather said propeller.

9. VA propeller control mechanism for a hydraulically adjustable constant speed propeller ofthe character described which comprises a propeller shaft, a housing rotatable with the propeller shaft, and providing a reservoir for receiving a quantity of pressure 'actuating fluid,an accumulator carried by the shaft, pressure developing means within said housing and operable upon rotation of said propeller for establishing a supply of fluid under pressure, a regulator valve within the housing for selectively controlling the Asupply of pressure fluid in response to change in speed of rotation from a desired value, conduit means extending between the pressure developing means and the regulator valve, and a trippable flow control valve mounted on the outside of said housing and opening into said conduit means for passing pressure uid from the pressure developing means to said accumulator, and including a trip mechanism for return flow of the pressure fluid from the storage chamber coincident with predetermined shift of the regulator valve, and nonrotating means located exterior of the housing and interconnecting with the regulator valve for modifying its control in response to change in propeller speed and selectivelt7 operable for actuating the said trip mechanism.

10. A propeller control mechanism for a hydraulically adjustable constant speed propeller which comprises an accumulator rotatable with the propeller, pressure developing means carried by the propeller and operable upon rotation of said propeller for establishing a supply of fluid under pressure, a regulator valve, rotatable with said propeller, controlling the supply of pressure fluid in response to change in speed of rotation from a desired value, conduit means extending between the pressure developing means and the regulator valve, and a trippable flow control valve rotatable with the propeller and connecting said accumulator and said conduit means for passing uid from the pressure developing means to said accumulator, trip mechanism for tripping said valve for return ow of the pressure fluid from the storage chamber, and non-rotating means interconnecting with the regulator valve for modifying its control and selectively operable for actuating said trip mechanism.

1l. In a controllable pitch propeller having l.pitch shiftable blades anda fluid operated system of control with blade motors for altering the blade angle, the combination of means for feathering the blades comprising, a pressure source developed by yrotation of the propeller, a cylinder mounted on the hub, a partition traversing the length of the cylinder and dividing it into a preloading chamber and a pressure chamber, passage means connecting the pressure chamber with the fluid operated system, a valve unit inserted into the passage means and operable to admit fluid to the pressure chamber upon rotation of the propeller, and means including a iiow valve selectively operable for opening the full charge of the pressure chamber to the nuid operated system whether or not the propeller is rotating, said flow valve comprising a housing, a main valve member reciprocable in said housing,

ERLE MARTIN. 2,296,288

JOHN E. ANDERSON. 213082-28 References cited Vin the V111e of this patent 2'391699 UNITED STATES PATENTS Number Name Date 10 Number 2,216,416 Mader Af oct. 1, 1940 480.4747 2,239,481 Christensen v 1 Apr. v22, l1941 '103,319

, I2 s Name Da'te Rindfleisch 1 Sept. 30, 19'41 VHerman May 19, 1942 Martin et al Sept. 22, 1942 Blanchard et 'a1 Jan. 5, 1943 Matteucci Jan. 12, 1943 Hanes e't a1 Dec. 25, 1945 4wmiziceN 'PTENTS Country VDate Great-Britain Sept. 25, 1938 Germany Y Sept. 6, 1941 

